Members of this family are related to RctB. RctB a protein of known structure but unknown function that often is encoded near RNA cyclase and therefore is suggested to be a tRNA or mRNA processing enzyme. This family of RctB-like proteins in encoded upstream of, and apparently is translationally coupled to, the putative peptide chain release factor RF-H (TIGR03072), product of the prfH gene. Note that a large deletion at the junction between this gene and the prfH gene in Escherichia coli K-12 marks both as probable pseudogenes.